The electrical and fossil fuel energy used in buildings and other spaces for heating and cooling comprises around 30% of all energy used in the USA and 40% of the electricity used, together with being totally responsible for the peak electrical loads in the summer that create blackouts. Much of this energy is originally from fossil fuel sources and the level of usage of fossil fuels is currently causing much concern. As ever more people throughout the world are looking to add air conditioning systems and as the climate continues to change with the increasing temperatures and humidity in the summer and the increasing cold snaps in the winter, this problem will only be exacerbated. In particular, current air conditioning is almost entirely powered by electricity which creates the peak electrical load that requires a high level of expensive peak power generation plant capacity. In September 2016, the USA and China signed the Paris agreement and just a couple of months before, the US Secretary of State declared at a UN meeting that air conditioning refrigerants were a bigger global threat than ISIS. It is time for a radically different approach to providing health and comfort to the indoor climate. Electricity developed from renewable sources or low use electric air conditioning can remove the peak electrical load.
The Laws of Thermodynamics warn against the use of higher energy sources to create lower energy sources as not only being wasteful but also very inefficient. Currently, fossil fuels are the high energy sources used to produce steam heat, which is a lower energy source, to drive turbine engines which generate electricity, a higher energy source. Fossil fuels themselves are raw energy sources that have taken considerable energy to produce, refine and convey to electric power plants. The electricity thus produced is moved along many miles of cables for use with electric motors that turn refrigeration compressors to create cooling in buildings. The total efficiency of this system may be only 10%.
Air conditioning by electrical compressors has difficulty in removing the humidity from the air in humid climates, particularly when dealing with 100% outside air. The process of dehumidifying through electric compressors involves supplying a cold enough chilled water or refrigerant to a cooling coil such that the air passing through the coil is cooled to below the dewpoint and moisture is condensed out of the airstream. This almost saturated air is then supplied to the space to be conditioned. The temperature of the air required to remove the preferred amount of moisture is so low that the extra electricity required may be a further 25%. This extra electricity will also be necessary if the system requires 100% outside air. Additionally, this leads to higher than preferred humidity in spaces and more recirculated air when the temperature outside is either hot and humid or cold and dry. This leads to poor indoor environmental conditions at the expense of energy conservation. A large quantity of primary energy supplied from fossil fuels and electricity results in waste heat, about 31% globally.
Most current heating, ventilating and air conditioning (HVAC) systems provide a minimum of outside air and have a mechanical particulate filter system. This filter system does not purify or sterilize the air supply nor does it remove unwanted gases and pollutants from the air supply. Recirculating the air through these systems may be a primary transmission method of colds, flu and other types of infections in buildings.
Many current HVAC systems provide very poor dehumidification during summer months and often no humidification during winter months so that the occupants may be uncomfortable almost year round. Many studies have shown that the discomfort of occupants along with maintenance complaints cause hundreds of billions of dollars in lost productivity yearly in the US. The health of building occupants may be compromised by the HVAC system such that transmission of diseases and the promotion of fungi, etc in the HVAC system and building are not prevented.
Desiccant-based dehumidifiers, such as Kathabar, have been introduced to the market on a number of occasions over the past 75 years but they have only achieved a very small market penetration and they have not been well received for a number of reasons, in addition to those previously mentioned. Firstly, they have been expensive to buy and any energy savings from their use has not been sufficient to payback the capital cost in a timescale considered economic to most building owners and operators. Secondly, the designs of first and some second-generation liquid desiccant systems were prone to allow micro droplets of the liquid desiccant to carryover into the building space served, which was highly undesirable because of contamination of the space and also the loss of the desiccant in the system.
Although several liquid desiccant type air conditioning systems have been developed, such as by AIL Research and DuCool, energy recovery has not been optimized. Once the systems are installed, there is no flexibility in where the used liquid desiccant (or working fluid) goes. It can all circulate to either a storage tank or into the regenerator storage, but there are no or too little other options which means that, even if some of the desiccant is still either highly concentrated, as in the cooling phase, or still highly diluted, as in the warming phase, it will still go the same path as more used liquid desiccant This is not the most efficient use of the liquid desiccant.
In such cases where a liquid desiccant is used, as in those systems already mentioned along with other systems such as those developed by 7AC, the flow pipe travels to the end of the flow and the return pipe travels from the end of the flow to the beginning of the flow pipe. This piping system is known as a flow and return system, the most common piping system used. This type of pipework steadily loses pressure through the flow pipe run which is at its lowest by the time it reaches the longest flow pipe, known as the index run. This is a very inflexible system as it is less possible to add more pads to the end of conditioner or regenerator and it is more difficult to balance if pads are removed. Therefore, the systems are inflexible for expansion or contraction and change of performance.
Current liquid desiccant air conditioning systems are not very flexible in sizing. Once the system is selected and installed, it is difficult to adjust the conditioner or regenerator to a larger or smaller air volume or vary the performance more than 10%. This is a limitation for the building owner as they thus must add additional units or run the system at the lower setting which is not the optimized system setting or purchase an entirely new system.
Current liquid desiccant systems, while able to be more efficient than conventional air conditioning refrigeration units, often still require quite low chilled water temperatures for cooling and quite high temperature heating for the desiccant regeneration process along with quite high heating temperatures in the winter for warming, while many do not offer a humidification option. Temperature differentials of 85° C. or more between chilled water temperatures and regeneration heating temperatures are often required. To attain such temperature differentials requires mechanical heating or cooling which requires more energy.
Maintenance is a huge problem with current HVAC systems and refrigeration systems. The over-complicated systems require too much maintenance and specialized technicians so that they are rarely subject to preventive maintenance. This lack of preventive maintenance creates energy inefficiency and an occupant comfort problem.
For the foregoing reasons, there is a need for a liquid desiccant air conditioning system that can answer all the problems building owners, building occupants and the over-stretched electric grid face.